1. Field of the Invention and the Description of Related Art
The present invention relates to an endoscope which is provided with a function of being locked to flexibility modifying operation member which is provided at an operation part.
In recent years, an endoscope has widely been used in which an elongated insertion part is inserted into a body cavity, to thereby observe an inspection objective part within the body cavity without the necessity of incision or excision and, under certain circumstances, to thereby use a treatment tool so as to be able to perform therapy and treatment.
The insertion part of the endoscope is so arranged as to have flexibility so as to be capable of being inserted into a bent or curved insertion path. There are cases, however, where, because of this flexibility, azimuth or direction of the forward-end side is not determined with respect to the hand side so that it becomes difficult to introduce the insertion part in the objective or a target direction.
In order to cope therewith, disclosed in U.S. Pat. No. 4,977,887, which serves as a first prior-art example, is an endoscope in which two helical tubes which are different in diameter from each other are provided in the insertion part, a rigidity controller which is provided at a grip part is operated to change a diameter of the inside helical tube whereby flexibility of the insertion part can be modified.
The prior-art example is of such a structure that a rearward end of the inside helical tube is moved spirally by operation of the rigidity controller and, thereupon, the diameter of the inside helical tube is modified as a whole. Accordingly, it is considered that it is extremely difficult to hold, to a uniform diameter, various portions of the insertion part.
Specifically, setting is made such that a striplike member which forms the inside helical tube is displaceable other than both ends thereof, and is formed spirally so that a diameter thereof is uniform. Even if a slight variation exists in characteristic thereof, however, the diameters thereof differ from each other. Further, when inserted into the body cavity, since forces which act upon a diameter of a portion thereof which is arranged within a curved curvature portion and a portion thereof which is arranged within a straight portion are different from each other, portions which are high in flexibility and portions which are low in flexibility are locally formed.
Moreover, even if adjustment or regularity is, first, made to have a uniform radius, the insertion part is inserted into the bent body cavity. Accordingly, if bending is repeated, the insertion part is apt to be deformed. Thus, it is made difficult to set the insertion part to flexibility uniform in a longitudinal direction of the insertion part, or the like. Accordingly, an endoscope is desired which can adjust the flexibility uniformly. Furthermore, this prior-art example has no lock mechanism to be described later.
For this reason, disclosed in Japanese Utility Model Unexamined Publication No. HEI 3-43802 (43802/1991) which serves as a second prior-art example is an arrangement which is provided with flexibility variable means which comprises a coil pipe and a wire, within the endoscope. According to the arrangement in this prior-art example, a compressive force can act relatively to the coil by operation to pull the wire, to modify the flexibility of the coil, an operator who perfonns an endoscope inspection can adjust flexibility of the insertion part by simple operation, and it is possible to facilitate insertion also into the bent path.
Since the wire which is arranged longitudinally of the insertion part is pulled to thereby compress the coil in the longitudinal direction of the insertion part, this second prior-art example can provide substantially equal compressive forces to various parts of the coil without being almost influenced upon a change in the diameter of the coil in a direction perpendicular to the compressive force. Thus, the second prior-art example can equally or uniformly adjust the flexibility longitudinally of the insertion part, by far, more than the first prior art example.
On one hand, the prior-art example requires considerably large or high capacity to pull the wire so as to have required hardness. An operation level of this prior-art example is not provided with a lock mechanism for, when the lever is operated to a certain hardness of the flexibility, holding the lever as a state of the hardness is required.
Accordingly, if a hand is removed from the lever which is operated under a hardened state, there is the possibility that the lever is naturally returned to an original position. This is useful when the insertion part is desired to be hardened instantaneously (volatility is desired to be raised). When it is desired, however, that the insertion part is inserted as the hard state is, such as the time of insertion into a depth of a large intestine, or the like, the lever must always be pressed down by the hand. Thus, operability is low.
Further, Japanese Patent Unexamined Publication No. HEI 5-91971 (91971/1993) discloses an endoscope which is provided with a flexibility modifying operation part at rearward ends of a coil and a wire which extends from an operation part.
Normally, the endoscope is of a structure in which a grip part which is provided in the vicinity of a proximal end of the operation part of the endoscope is gripped by an operator, and operation such as curvature or the like can be performed by the gripped hand. For this reason, in the above-described prior-art example, since the flexibility modifying operation part is provided at a position which extends from the operation part, the gripped hand must be removed from the operation part and be operated so that the flexibility is made variable. Thus, an arrangement which improves operability is desired.